A342902 a(n) is the smallest number that is the sum of n positive cubes in two ways.

1729, 251, 219, 157, 158, 131, 132, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126

Offset

2,1

Comments

This is r(n,3,2) in Alter's notation.

Links

Table of n, a(n) for n=2..63.

R. Alter, Computations and generalizations on a remark of Ramanujan, pp. 182-196 of "Analytic Number Theory (Philadelphia, 1980)", ed. M. I. Knopp, Lect. Notes Math., Vol. 899, 1981. See Table 2, page 190.

Index entries for linear recurrences with constant coefficients, signature (2,-1).

Formula

a(n) = n+63 for n >= 9.

Example

a(2) = 1729 = 12^3 + 1^3 = 10^3 + 9^3 (the famous Hardy-Ramanujan number).
a(3) = 251 = 5^3 + 5^3 + 1^3 = 6^3 + 3^3 + 2^3.

Crossrefs

Cf. A001235, A011541, A230563, A342903, A343077, A343078, A343079, A343081, A343085.

Sequence in context: A013797 A344744 A013864 * A112140 A044883 A288153

Adjacent sequences: A342899 A342900 A342901 * A342903 A342904 A342905

Keyword

nonn

Author

N. J. A. Sloane, Apr 03 2021

Status

approved